You do not need a visa to enter Canada because you have a UK passport. At the border you should be clear that you are just visiting. Have a return ticket with a specific date; you can always change it later. Bring proof of ties to the UK, such as proof of a job, a lease or mortgage, bank information, etc. If you don't have any of this, well, they might not ask to see it anyway. At least have proof of funds for your trip.
If they ask about marriage, be honest.
The border agent can refuse you entry if he or she believes you will not return to the UK, or if he or she believes you will work. They can also give you a reduced stay - in which case, they will stamp a date on your passport. If you do not get a stamp with a limited stay, you have six months. This can be extended about one month before the stay is supposed to be over.